A major goal of this grant is to elucidate the underlying molecular and cellular mechanisms for the induction and regulation of antigen-specific secretory IgA (S-IgA) immune responses at mucosal surfaces with emphasis on salivary gland. The induction of S-IgA antibodies is an important arm of the immune system and is considered to be a major first line of defense against invasion of pathogenic microorganisms through the mucosal surface area. Since saliva is a prominent example of an external secretions containing S-IgA, it is important to examine the immunological mechanisms for the induction and regulation of this important defense factors in mucosa-associated tissues, with emphasis on the salivary glands. To this end, our overall hypothesis is that a mucosal T cell internet exists where gamma-delta, alpha-beta T cells and acinar/ epithelial cells and their derived cytokines as well as cell-to-cell contact all play an major role in the induction and regulation of antigen-specific S-IgA antibodies responses. Thus, this mucosal T cell and acinar / epithelial cell internet may be a key element which bridges acquired and innate immunity for the development of a protective defense at mucosal surfaces. For the purpose of accomplishing our major goal, this grant proposal consists of five specific aims. Our emphasis will be focused on the molecular and cellular mechanisms for the induction and regulation of antigen [e.g., ovalbumin (OVA)] -specific IgA synthesis by the mucosal T cell internet. Thus, we will use well known mucosal adjuvant, cholera toxin (CT) in order to induce antigen-specific S-IgA responses in salivary gland for this grant application. Especially, genetically manipulated mutant CT will be a focus of the grant in order to compare the modulation of Th1- and Th2-type cytokine production for the induction of antigen-specific mucosal IgA and systemic IgE immune responses to wild type CT. The role of gamma-delta T cells for the regulation of mucosal IgA and systemic IgE will also be investigated. In particular, our specific aims are divided into the following five components. The first aim is the assess of genetically manipulated CT for mucosal adjuvant activity to induce antigen-specific S- IgA responses in saliva and submandibular gland (SMG) ; the second aim is characterize of antigen (OVA) -specific CD4+ Th1 and Th2 cell responses induced in SMG by intranasal immunization with OVA plus CT mutants as mucosal adjuvants; the third aim is to test whether salivary gland acinar /epithelial cells and / or gamma-delta T cells can regulate CD4+, alpha- beta T cells for the expression of Th2-cytokines (e.g., IL-5 and IL-6) for antigen-specific IgA B cell responses; the fourth aim is to; determine possible mechanism(s) for triad cell-to-cell interactions among acinar /epithelial cells, gamma-delta T cells and CD4+, alpha-beta T cells via cytokine(s) and cell surface molecule(s); the fifth aim is to examine the contribution of gamma-delta T cells for the regulation salivary IgA and systemic IgE responses using TCRdelta and TCRbeta gene disrupted mice.